1. Field of the Invention
This invention relates to masks for semiconductor manufacturing and more particularly to phase-shifting masks.
2. Description of Related Art
This invention teaches an electronically controlled universal phase-shift mask in a stepper exposure system. The pixel dynamic mask e.g., a SLM (Spatial Light Modulator) can be controlled to have phase-shift features.
Pfauler et al. "High-Throughput Optical Direct Write Lithography", Solid State Technology (June 1997), pp. 175-176, 178, 180, 182 describes a direct write lithography system using a programmable phase-modulated spatial light modulator (SLM) system in which the image is reflected from the SLM onto a semiconductor wafer. The spatial light modulator comprises an array of rectangular electrodes with a reflective, deformable viscoelastic layer on top. The SLM serves as a plane mirror in an optical system.
U.S. Pat. No. 5,641,937 of Nelson for "Method for High Resolution Printing" shows an SLM in a printing system.
U.S. Pat. No. 5,600,485 of Iwaki et al. for "Optical Pattern Recognition System and Method of Ferroelectric Liquid Crystal Spatial Light Modulator" shows a pattern recognition system using a SLM (spatial light modulator).
U.S. Pat. No. 5,724,447 of Fukushima for "Optical Transform System for Three-Dimensional Object Recognition" shows an image detection system for phase-shift masks using an SLM and a CCD.
Levenson et al "Improving Resolution in Photolithography with a Phase-Shifting Mask", IEEE Transactions on Electron Devices, VOL. ED-29. No. 12, (December 1982), pp. 1828-1836.
Levenson "Phase-Shifting Mask Strategies: Isolated Dark Lines", Microlithograpy World, (March/April 1992) pp. 6-12).